Method of preparation of barium soap greases



Patentecl Sept. 28, 1948 S PATENT #oFFieE METHGD OF- PREPARATION 3 OF BARIUM SOAP 'GBEASES .UNITE'D STATE I 641-4) Relating the 'VGC to' the process of the "--in-vention it was found that the saponification should be 'condu'cted in the presence of anaph- "'IZThis inventiorfrelates to improvements in the manufacture and production of lubricating grease ""compositions"and particularly to improvements inthe'manufacture of stable barium soap greases.

-=thenic oil-possessinga VGC of at least ;8'70.

Although barium soap greases have been recog- 5 -It wasalso fourrdthat upon cooling thebarium ".nized as'a'desirable adjunct to the more convensoap base following dehydration:thestructure of tiona'l line oflubricating greases by virtue of their the base -undergoes acomplete- 'phase" change. inherent properties of water resistance and com- This transition ofstructure is manifeste'd in the parat'ivelyiihigh "dropping points, their general appearance of the grease base which "changes Tappli'oation has been retarded because of the from a homogeneous gel-like "structure to an inhomogeneous dry cr'umbly mass': The particular' temperature range over which this transil--have'con'cluded that the desirable characteristics --ti on occurs-'isdependentupon and varieswith the f 'of barium soap greases are attained by the basic 'acid component ofthe barium soap and-fwill be 'and/orcomplexbarium soap greaseswhich can referred to'in the'following' descriptionand the only be prepared by a complicated method of claims as-the critical transition temperature of manufacture involving intricate compounding the grease-basa At-this' critical-transition temprocedures and special cooling and milling operaperaturethegrease base loses its grease= strucjtions. It has been the experience of the prior -ture-ari'dif-worked -up in -theconven'tionalmanart that the preparation of the'normal-barium '-ner;--would-resu1t in an 'irihomogeneous product soap greases was even more difficult and required tl1'at-cannot'be broughtto'g'ether even after extenw-Water for stabilization, which substantially nulli- -sivemil1ing2 This m'ay be avoided,"however by fled any improvement over the conventional calmaintaining the concentration of the barium cium soap greases. soap in-"the grease base at .least= greater. than It has now been found possible to prepare: approximately 40% and continuously stirrin'g the barium-soap greases by a simple and economical T'- dehydrated base while 'cooling through the critimethod which avoids the use of complicated *"cal transition temperature range-untiLthe grease -manufacturing techniques and can easily be *ba'se 'revertsback to a"'homogeneou's "taffystruccarried-out in' conventionalsteam-heated equip- ----=ture. ""-=ment.-- Although this discovery may be generally According to the-process of the invention applied to all-barium soap greases, including the 1 barium soap greas'es may be prepared by 's'abonimixedbasegreases in which barium is one of the "dying a soap-forming:fatty -acid with barium metal components, it is particularly'applicable to -'-*-hydroxide orhydra't'e in the presence of a inaphthe normal barium soap greasesand affords a '-'-thenic mineral oil '--possessing a viscosity gravity allegedlimitations in composition and attendant ""iidifliculties in'ma nuiacture. 'Prior investigators 'method of'preparing a stable, normal barium soap ""con'stant VGC) of at least 0.370 to effect solvagrea'se without the aid of water or other added *tion oftheresulting bariumsoap. The '.saponif stabilizers. -fication product is then dehydrated at a tempera- "improved method of preparing barium 'ture not in exces's ofthe'melting point 'o'f thesoap soap grea'ses is dependent upon two important base and'prefer'ably at temperatures o'f approxi- 'features" of-- the invention, namely, the presence 40=mately 300 to 320 F After dehydration is sub-- ofa naphthenic oil during the saponification of stantia1ly-compiete the 'product is cooled with 'the fatty acid material and the stirring down of continuous stirring without the addition of'subthe dehydrated grease base while cooling to a stantial amountsof lubricating oil; Thestirring temperature below the critical transition temdown of=the dehydrated soap-base is continued perature of the grease base. until a 'com-plete ploas'e ch'a'nge in the soapbase Since there is no clear line of demarcation structure has been obtained. Thi'sphase change *betweennaphthenic and paraffinic oils and the or -tr-ansition' of thesoapstruc-ture isusually 'naphthenicity or parafiinicity of an oil is a matter 7 completed at-around 200 F. It is particularly -'of--degree, reference will be made to the viscosity desirable to maintain =the soapLconcehtration at gravity'constant (VGC) of the oil. The VGC is; -least greater athan. approximatelyr40% and-prefan arbitrary constant calculated from the Sayerably around 50"%' duringthe stirring downand bolt Universal viscosity and the specific gravity pooling-operation.

of an oil,'the value of which increases withnaphi The appearance of the" grease zbasestructure thenicity and decreases'with paraffinicity (Hill will vary somewhat with the type'of' -ifattywacid l -&-Coats'; -Ind.*& Eng. Chem.-, vol; 20, 1928 1 3; used for' saponificatiom IWheni using :the conventional saturated fatty acids as the acid component of the soap base a tough rubbery gel is obtained on dehydration which then changes on stirring and cooling to a dry crumbly mass and finally comes around to a tough sticky mass. It is requisite that this complete transition of structure be completed before any substantial addition of lubricating oil since oil addition at any point prior to the complete transition results in an inhomogeneous grease containing hard soap lumps which cannot be brought together. After the completion of the phase change of the grease structure, the mineral lubricating oil may be incorporated until the desired consistency is reached and the final grease composition drawn from the kettle.

Throughout the preparation of the grease composition it is desirable to maintai continuous stirring. During the cooling stage, when the concentration of the soap is approximately 50% or greater considerable load is applied to the stirring mechanism and if the stirring mechanism becomes overloaded it may be desirable to incorporate small amounts of the mineral lubricating oil to reduce the load on the stirring mechanism. The addition of the mineral oil at this stage should be controlled so that the concentration of the soap is not reduced to substantially below 40%.

Although any conventional fatty acid material may be used as the acid component of the barium soap, the best yields and quality of grease are obtained by charging fatty acids or mixtures thereof and particularly fatty acids containing at least 16 carbon atoms or predominating amounts of fatty acids of at least 16 carbon atoms. Glycerides such as are contained in the natural fats may be used provided the free glycerin formed on saponification is substantially removed by steam distillation or by prolonged heating in the dehydration stage. Examples of the fatty acids found suitable for the preparation of the barium greases include such acids as stearic, palmitic, behenic, oleic, hydroxy stearic, etc.

As has been previously mentioned, a naphthenic mineral oil possessing a VGC of at least 0.870 is required to effect solvation of the barium soap formed in the saponification stage of the process. This naphthenic mineral oil may be either a distillate or residual lubricating oil of the desired viscosity or may consist of a blend of lubricating oils in which the VGC of the final blend is at least 0.870. The amount of the naphthenic mineral oil charged in the saponification stage is not critical to the invention but for ease of manufacture it is preferable to employ approximately an equal weight of mineral oil based upon the weight of the fatty acids charged. After the saponiflcation further processing and finishing of the grease base may be conducted with any of the conventional lubricating oils, irrespective of the naphthenicity or paraffinicity of the oil.

Contrary to the experiences of the prior art the proces of the invention permits the preparation of stable barium soap greases and particularly normal barium soap greases without limitations in composition requiring the addition of water or the presence of free fatty acid to effect stability. According to the present process barium soap greases can be prepared neutral or containing free acid or free alkali, as desired, without producing any adverse effect on the stability of the product.

The following example is presented as an 11-.

lustration of the method of preparing a normal barium soap grease in accordance with the procass of the invention.

Example 310 grams of stearic acid and 372 grams of a naphthenic Pale Oil possessing a S. U. V. at F. of 312 and a VGC of 0.884 were charged to a grease kettle. The stearic acid was melted at 210 F., at which temperature 563 grams of a hot aqueous solution of barium hydroxide (17.6% Ba(OH) 2) were added followed by 50 ml. of water. This mixture was stirred at 210 F. for one-half hour after all the water had evaporated. The temperature was then raised to 310 F. in 25 minutes and held at this temperature for 15 minutes, at which point the grease base was a stiff, taffy-like mass and rather rubbery. The heat was then removed and the mass stirred with natural cooling, the temperature reaching 200 F. in approximately 1 hour and 50 minutes. During the cooling period the appearance of the grease base changed from a stringy, taffy-like mass to a dry and flaky mass at about 240 F.

Further cooling and stirring resulted in a stiff,

grainy dough at about 230 F.. which became a smooth, pasty mass entirely devoid of lumps, as the temperature decreased. The grease base was maintained at 200 F. for about 15 minutes, after which 1928 grams of Pale Oil was gradually incorporated with continuous stirring. After the oil addition was complete the grease composition was stirred an additional 15 minutes and the transparent reddish grease withdrawn from the kettle. The tests on the final grease composition were as follows:

Barium soap, percent (calculated) 14.0 Free alkali (as Ba (OH) 2), per cent 0.08 Free fatty acid (as oleic) per cent 0.10 Dropping point, "F (ASTM) 293 Penetration, 77 F. (ASTM) r Unworked 207 Worked 277 1 The Institute Spokesman, National Lubricating Grease Institute, January, 1944. Test Methods for Determining Free Acid and Free Alkali in Greases.

Obviously many modifications and variation of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of preparing a normal barium soap grease composition which comprises saponifying a soap-forming fatty acid with not more than the stoichiometric equivalent of barium hydrate in the presence of a mineral oil possessing a VGC of at least 0.870 to produce a saponification product of normal barium soap, dehydrating the saponification product at temperatures not in excess of the melting point of the soap base, cooling the dehydrated product with continuous stirring to a temperature below the critical transition temperature of the grease base without reducing the concentration of the soap component to substantially below 40%, thereafter adding mineral lubricating oil to obtain the desired consistency and drawing the resulting grease composition.

2. A method of preparing a normal barium soap grease composition which comprises saponifying a fatty acid containing at least 16 carbon, atoms with substantially the stoichiometric quantity of barium hydrate in the presence of a mineral oil possessing a VGC of at least 0.870 to produce a saponification product of normal barium soap, dehydrating the saponification product at temperatures not in excess of the melting point of the soap base, cooling the dehydrated product with continuous stirring to a temperature of approximately 200 F. without reducing the concentration of the soap component to substantially below 40%, thereafter adding mineral lubricating oil to obtain the desired consistency and drawing the resulting grease composition.

3. A method of preparing a normal barium soap grease composition which comprises saponifying a fatty acid containing at least 16 carbon atoms with barium hydrate, in stoichiometric quantities required for the preparation of a normal barium soap, in the presence of a mineral oil possessing a VGC of at least 0.870, dehydrating the saponification product at temperatures not in excess of the melting point of the soap base, cooling the dehydrated product with continuous stirring to a temperature below the critical transition temperature of the normal soap base without reducing the concentration of the normal soap component to substantially less than 40%, thereafter adding mineral lubricating oil to obtain the desired consistency and drawing the finished grease composition.

4. A method of preparing a normal barium soap grease composition which comprises saponifying a fatty acid containing at least 16 carbon atoms with substantially the stoichiometric quantity of barium hydrate in the presence of sufiiicient mineral lubricating oil possessing a VGC of at least 0.870 to effect solvation of the resulting normal barium soap, dehydrating the saponification product at temperatures of approximately 300-320 F., cooling the dehydrated product with continuous stirring to a temperature of approximately 200 F. without reducing the concentration of the soap component to sub s-tantially below 40%, thereafter adding mineral lubricating oil to obtain the desired consistency and drawing the resulting grease composition.

5. A method of preparing a normal barium soap grease composition which comprises saponifying a fatty acid containing at least 16 carbon atoms with not more than the stoichiometric equivalent of barium hydrate in the presence of approximately equal weights, based upon the weight of fatty acid, of a mineral oil possessing a VGC of at least 0.870 to produce an oil solu tion of normal barium soap dehydrating the saponification product at temperatures not in excess of the melting point of the soap base,

cooling the dehydrated product with continuous 6 stirring to a temperature of approximately 200 1". without reducing the concentration of the soap component to substantially below thereafter adding mineral lubricating oil to obtain the desired consistency and drawing the resulting grease composition.

6. A method of preparing a normal barium stearate grease composition which comprises saponifying stearic acid with not more than the stoichiornetric equivalent of barium hydrate in the presence of a mineral oil possessing a VGC of at least 0.870 to produce normal barium stearate, dehydrating the saponification product at temperatures not in excess of the melting point of the soap base, cooling the dehydrated product with continuous stirring to a temperature of approximately 200 F. without reducing the concentration of the barium stearate to substantially below 40%, adding mineral lubricating oil to obtain the desired consistency and drawing the resulting grease composition.

7. A method of preparing a normal barium stearate grease composition which comprises saponifying stearic acid with substantially the stoichiometric quantity of barium hydrate in the presence of about an equal quantity based on the stearic acid of a mineral lubricating oil possessing a VGC of at least 0.870 to produce an oil solution of normal barium stearate, dehydrating the sapqnification proctuct at temperatures above 300 F. but not in excess of the melting point of the soap base, cooling the dehydrated product with continuous stirring to a temperature of approximately 200 F. without reducing the concentration of the barium stearate to substantially below thereafter adding mineral lubricating oil to obtain the desired consistency and drawing the resulting grease composition.

ERIC A. BERGMANN. HARRY V. ASI-IBURN. GEORGE W. ECKERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,033,148 Ott, et a1 Mar. 10, 1936 2,070,781 Brunstrum, et a1. Feb. 16, 1937 2,154,383 Ott, et a1 Apr. 11, 1939 2,417,433 McLennan Mar. 18, 1947 OTHER REFERENCES McLennan, Methods of Compounding Barium Greases, Their Properties, Uses and Future- Article in National Petroleum News, April 5, 1944, pages R 234, R 236, R 238, and R 239. 

